«بَرَقَتْ أَسَارِيرُ مَسَرَّتِهِ»
The signs of his happiness flashed across his face.
Asārīr concerns facial lines or features, while masarrah is joy. Baraqat makes that joy appear like a quick flash of light.
Al-Ḥārith truly observes delight on Abū Zayd’s face. The narrative does not yet state what kind of satisfaction it is—relief for a family, or pleasure at a successful ruse. The next exchange will resolve the ambiguity.